Module metrics

MQTT Broker Performance Monitoring System

Provides comprehensive metrics collection with:

• 50+ operational metrics
• Thread-safe atomic counters
• Categorized event tracking
• Serialization support

Metric Categories

1. ​​Client Lifecycle​​:

   • Authentication attempts/successes
   • Connection establishment
   • Subscription management
   • ACL verification

2. ​​Session Tracking​​:

   • Creation/resumption
   • Subscription changes
   • Termination events

3. ​​Message Processing​​:

   • Publish/delivery/ack flows
   • Message drops
   • Non-subscribed messages
   • QoS-specific tracking

4. ​​Message Types​​:

   • Custom messages
   • Admin messages
   • Last Will messages
   • System messages
   • Bridge messages
   • Retained messages

Key Features

• Atomic counters for thread safety
• Automatic derive macros for metrics operations
• Serde serialization support
• Zero-overhead when disabled
• Categorized counters for detailed analysis

Implementation Details

• Uses AtomicUsize for lock-free counting
• Macro-generated metric operations
• Organized by logical categories
• Designed for monitoring systems integration

Usage Patterns:

1. Increment counters at relevant code points
2. Serialize for external monitoring
3. Analyze trends across metric categories

Note: All metrics are optional - only enabled counters incur measurement overhead.

Structs

Metrics